This song obviously has two different Sections. The first has 8 Elements. Although they are fairly fast, they are slow enough to be very distinct and it’s possible to imagine counting the number while it’s singing. The Elements are somewhat emphatic and bright, as they are Expanded and cover a large frequency range.
The second Section is lower, and way too fast to count; a trill. The pitch is fairly stable during both Sections.
It turns out this speed difference between the first and second Sections is an important clue.
Let’s first examine Orange-crowned Warbler’s song.
Many Orange-crowned songs have a similar form: 2 Sections, the second lower. However the speed is much different. Both Sections are so fast that it would be impossible to imagine counting the number of Elements. This characteristic: that all Sections of this species’ songs are sung at trill speed is a very good ID point.
Also, the pitch tends to drift and, in general, the Elements are less Expanded and thus less emphatic.
Based on these characteristics we can rule out Orange-crowned.
Nashville also has a similar song form: 2 Sections, the second lower.
However Nashville’s first Sections are quite different. Instead of short, fairly emphatic 1-Element Phrases, Nashville’s songs are almost always 2-Element Phrases. And the Phrase speed is considerably slower. This more deliberate speed, with 2-Element Phrases, makes it easy to separate Nashville from this song.
That leaves Wilson’s Warbler. Wilson sings a fairly wide range of songs. Many are only 1-Section, often falling in pitch towards the end. They also sing 2-Section songs like our target song.
The key point is that the first Sections are fairly emphatic Phrases that are never fast enough to be a Trill. And although they can be somewhat intricate, the Phrases are never made up of 2 separate, repeated Elements.